Intercept valves are generally located in a conduit and when activated by means for activating are able either to allow or interrupt passage of a fluid flowing internally of the conduit, with a simple on-off mechanism of either complete opening or complete shutting.
In the field of spray guns in water spray equipment, the fluid crossing the valves is conveyed under very high pressure, which can be up to 350 bar. Consequently the design of the valves is such that much attention has been paid not only to guarantee good operation at pressures which can go above the above-mentioned reference values, but also to provide a long working life. The prior art includes, for example, European patent No. EP0572237, which teaches a spray gun provided with a double-acting valve activated by a trigger. This solution is not adaptable to the field of water-spray guns, since the latter operate at high pressure and delivery rates and must marry simplicity of assembly with low weight, and also offer very good leak-proof characteristics. Another known solution is U.S. Pat. No. 5,913,505, which includes a lever system of on-off activation of the valve.
This system too, which exhibits coaxial fluid inlet and outlet, cannot be applied on water spray guns since it has the drawback of being constructionally very complex, having a high number of components and being rather unwieldy. Further, a spray gun fitted with a device of this type for fluid interception would lose its characteristic of ready response to valve opening and closure.
Also known in the prior art are fluid passage regulation valves, such as for example U.S. Pat. No. 3,525,359, which with a discrete movement of a pivot on an obturator the fluid can be regulated in output.
This solution is not usable on water guns because apart from the fact that they do not exhibit coaxial fluid inlet and outlet, limiting the load losses, in this type of gun a sharp interception of the fluid is required, a characteristic which is unobtainable with a discrete movement of a pivot on an obturator.
The Applicant designed an intercept valve with a spherical obturator, in Italian patent application no. RE2002A000102.
This valve, which is interpositioned between a tube from which the jet of fluid exits and a further supply tube, coaxial to the first, exhibits an internal cavity in which an spherical obturator is arranged, which obturator abuts on a fluid passage seal and is subjected to the action of a manually-operated pushing element.
The hydrostatic force of the pressurised fluid causes a thrust on the spherical obturator which favours closure of the conduit on which the valve is located, while the activation of the pusher, by acting on the obturator, enables the conduit to open.
Following prototype construction and testing the Applicant's product displayed some drawbacks.
The continuous dragging of the obturator, which is made of metal, on the seal, which is made of plastic, following opening and closing of the valve, causes wear and leads to damage on the contact surface of the seal.
This phenomenon is made worse when the fluid contains suspended abrasive substances.
Taking into account that spray guns for washing apparatus are usually capable of working at high and low fluid pressures, wear on the seal can present a further drawback.
Though at high pressure the hydrostatic force generated by the fluid enables closure of the obturator on the albeit worn seal, at low pressure the hydrostatic force generated is not sufficient to guarantee a perfect seal of the obturator on the worn seal, the result being a loss of fluid even when the valve is closed. The main aim of the present invention is to adapt a fluid intercept valve which is provided with an obturator that does not generate wear on the seal it abuts. A further aim of the present invention is to provide a fluid intercept valve which is provided with an obturator that can reduce the force needed to commute the valve from the open position to the closed position in comparison with other valves.
A further aim of the invention is to provide a fluid intercept valve which enables a variation of the force needed to displace the obturator into the open position during design stage, by modifying the point of application of the pushing element and consequently the longitudinal development of the obturator.
The technical objective and set aims are all attained by the fluid intercept valve, which is characterised in that it comprises one or more of the technical solutions claimed herein below.